Nurses at the Neonatal Intensive Care Unit at New York University's Langone Medical Center have challenging jobs, even in the best of times. Their patients are babies, some weighing as little as 2 pounds, who require constant and careful care as they struggle to stay alive.

On Monday night, as superstorm Sandy bore down on Manhattan, the nurses' jobs took on a whole new sense of urgency as failing power forced the hospital's patients, including the NICU nurses' tiny charges, to evacuate.

"20/20" recently reunited seven of those nurses: Claudia Roman, Nicola Zanzotta-Tagle, Margot Condon, Sandra Kyong Bradbury, Beth Largey, Annie Irace and Menchu Sanchez. They described how they managed to do their jobs – and save the most vulnerable of lives – under near-impossible circumstances.

On Monday night, as Sandy's wind and rain buffeted the hospital's windows, the nurses were preparing for a shift change and the day nurses had begun to brief the night shift nurses. Suddenly, the hospital was plunged into darkness. The respirators and monitors keeping the infants alive all went silent.

For one brief moment, everyone froze. Then the alarms began to ring as backup batteries kicked in. But the coast wasn't clear – the nurses were soon horrified to learn that the hospital's generator had failed, and that the East River had risen to start flooding the hospital.

"Everybody ran to a patient to make sure that the babies were fine," Nicola Zanzotto-Tagle recalled. "If you had your phone with a flashlight on the phone, you held it right over the baby."

For now, the four most critical patients – infants that couldn't breathe on their own – were being supplied oxygen by battery-powered respirators, but the clock was ticking. They had, at most, just four hours before the machines were at risk of failing.

Annie Irache tended to the most critical baby -- he had had abdominal surgery just the day before – as an evacuation of 20 NICU babies began.

"[He] was on medications to keep up his blood pressure," Irache said, "and he also had a cardiac defect, so he was our first baby to go."

One by one, each tiny infant, swaddled in blankets and a heating pad, cradled by one nurse and surrounded by at least five others, was carried down nine flights of stairs. Security guards and secretaries pitched in, lighting the way with flashlights and cell phones.

The procession moved slowly. As nurses took their careful steps, they carefully squeezed bags of oxygen into the babies' lungs.

With their adrenaline pumping, the nurses said, it was imperative that they stay focused.

"We're not usually bagging a baby down a stairwell ... n the dark," said Claudia Roman. "I was most worried about, 'Let me not trip on this staircase as I'm carrying someone's precious child, because that would be unforgivable."

When the medical staff and the 20 babies emerged, a line of ambulances was waiting. A video of Margot Condon cradling a tiny baby as she rode a gurney struck a chord worldwide. But Condon said she had a singular goal.

"I was making sure the tube was in place, that the baby was pink," she said. "I was not taking my eyes off that baby or that tube."

Like other nurses, she did not feel panic. Her precious patient helped keep her calm.